Heavy media separation process



Oct. 23, 1945. V, D. B. GROVE Y 3 HEAVY MEDIA SEPARATION PROCESS Filed Aug. 29, 1942 0 & K h E Q0 .3 0' b E u I E 3 I I INVENTOR g Q 041//0 5. G/POI/', g 3 BY q 3 k E TT 'RNEY Patented. Oct. 23, 1945 David B. Grove, Mascot, Tenn.,

assignor to MineralsBeneficiation, Incorporated, Joplin, Mo., a corporation of Delaware Application August 29, 1942, Serial No. 456,584 3 Claims. (Cl. 209-173) This invention relates to an improvement in the heavy media separation of ore constituents.

In the ordinary process of ore concentration using heavy media, the ore-containing components of different specific gravities and sized to a certain range are introduced into a suitable separating chamber frequently conical in shape which is filled with a heavy density medium produced by suspending finely divided parts of high specific gravity to produce a concentrated suspension. The light constituents of the ore float to the top and overflow together with some of the medium and the heavy particles sink to the bottom where they are removed together with adherent heavy density medium with air lifts or suitable elevating mechanisms.

Heavy density separating processes have achieved great pratical importance as they represent exceedingly cheap and eflective separating processes. However, the applicability of the process has been to some extent restricted because the feed has to be careiullysized. The bulk of the medium returned to the top of the tank for the purpose of transporting the floating particles is suflicient to entrain fine particles 01' heavy mineral which, because of their lower settling rate, have insuflicient time to settle out of the continuous flow or medium required for high capacity in the tank. In the majority 01' ore dressing opera-- tions the barren gangue constitutes the low specific gravity component; and the high specific gravity component normally represents desired values. Even in the treatment of coal, which is an exceptional case, where the light material is valuable and the heavy material is waste it is important to obtain the light material with a minimum contamination of heavy material in order to obtain coals of desired low ash content.

product of the main separating tank. The invention will be described in connection with the drawing which is a diagrammatic representation of a plant utilizing the features oith'e' present invention. The showing in the drawing is purely V diagrammatic as for the most part individual structural design of the component apparatus forms no part of the present invention which con- The difficulties encountered in the treatment of ores where there are fine particles oi high specific gravity material have imposed a serious limitation on the process because it has been necessary'to size' the feed fairly closely and no equally cheap means has been available in most cases for the treatment of flner heavy density material which may be formed in crushing oi the ore to produce the feed. Considerable quantities or useful material have thus been wasted and it is an object or the present invention to recover in a more or less complete manner these finer particles of high specific gravity material which were hitherto lost.

This object is eirected by means of the process of the present invention by separating the fine high specific gravity material from a coarser floating material and returning it to the sink templates an organization of apparatus broadly and a process.

In the drawing the main separatory tank is shown in the form of a conventional heavy density medium cone I. This cone may be filled with asuspension of high specific gravity particles of galena, magnetite, ferrcsilicon and the like in a sufllcient water to sired specific gravity. Into this medium is fed the ore to be treated in the conventional manner, the ore being introduced on the surface 01' the cone'as is customary. The ore is roughly sized and contains fine high specific gravity material as well as the customary coarsesizes which are normally used in processes of this type. The finely divided high specific gravity particles are for the most part considerably coarser than the particles constituting the heavy density medium itself.

A sink and float separation takes place in the usual manner, the light particles floating to the topof the cone and overflowing on to a screen 2 while the heavy coarse particles sink to the bottom of the cone where they are removed by the air lift 3 and are the fine drainage screen 2 not only medium itself and also some of the ticles. that only particles a fine as the heavy medium particles pass through. The medium thus drains into a cleaning cone 5 having an air lift for elevating the heavier material 6 which returns this material through the pipe I to the main separating cone l.

Screen 4 is of a size comparable to that of screen 2 and also drains medium, this time di rectly back into the cone. The sink product from screen 4 with some adherent medium is then dis-= charged onto screen I 2 and similarly the finer high specific gravity particles are discharged from screen 2 onto screen 8. Both of these screens are provided with suitable Water sprays i3! and I4 respectively towash ofl adherent medium. Howevenscreen I2 is of substantially the same screen 4. The overflow onto the light floating particles but finer high specific gravity parflneness as screens 2 and l and therefore only produce a medium of the deelevated and discharged on to contains the particles oi the The screen size is kept sufficiently fine so washed medium passes through to the conventional cleaning. Screen 8, however, and this is the principal feature of the present invention, is

provided with holes just small enough to insure the retention thereon of the normal float product. In a typical plant the openings of this screen may be of the order of .27 of an inch, the exact size depending upon the nature of the ore feed. As a result the solids washed through this screen contain not only particles of the medium itself but also fine particles of high specific gravity material which had insumcient falling velocity in the viscous heavy medium to sink to the bottom of cone I. This drainage passes through line 9 to the bucket elevator ll where it is raised and dropped onto the concentrate washing screen l2 and finally joins the concentrates discharged from the top of the screen. This latter underflow from screen 8 is joined by the overflow from the cleaning cone 5 which passes through the line Ill. The overflow contains medium particles contaminated with any fine low specific gravity material and as a result the medium return through the line I is clean. The fine low density material mixed with medium particles all flows through the screen i2 and passes to the medium cleaning plant where suitable steps are taken to remove any fine low specific gravity material. The design of the medium cleaning plant forms no part of the present invention and any suitable cleaning scheme may be employed. 2

It will be noted that the present invention does not disturb the ordinary functioning of the heavy medium process and that the minor additional cost of the small cleaning cone 5 and the placement of the coarser size, cheaper screen mesh on the washing screen 8 permits recovering fine high specific gravity material and at the'same time prevents accumulation of finely divide'd low specific gravity material in the separating medium itself. Not only are these advantages obtained without i pensive additional equipment but the general organization of the heavy media separation process is not disturbed so that the present invention can be readily applied to existing plants. In the case or the present invention no new operating technique need be learned. 4

As has been pointed out above particular technical structural features do not form any part of the present invention which is an advantage but in practice the best designs for individual elements will normally be employed and in particular any special shape of separating chamber which is desirable with a particular ore may be employed. I claim:

1. In a method of concentrating mixtures of minerals of different specific gravityderived from -liquid, the particle size of the fine particles of high specific gravity mineral being sufliciently fine so that at least a portion of them do not sink in the medium but being coarser than the particle size oi! the medium solids themselves. the improvement which comprises recovering heavy particles which sink through the medium, overflowing a portion of themedium' together with floating particles of light specific gravity and fine particles of heavy specific gravity, subjecting said overflow to a screening operation whereby particles of medium are removed from the floated particles of the mixture, subjecting the residue to a second screening operation whereby the coarse material of low specific gravity in the float product is separated from the fine high specific gravity material and from medium solids adhering there. subjecting the mixture of medium solids an flne particles of high specific gravity to a screening operation eflecting separation at an intermediate size, returning the me- .dium particles to the separating medium substantially tree from fine high specific gravity materials and recovering the separated fine high specific gravity materials.

2. A method according to claim 1 in which the screen underfiow from the first screen op-' eration is subjected to a specific gravity separation whereby a portion of the drained medium overflows together with the fine low density material and mixing said overflow with the screen undersize from the second screen.

3. A method according to claim 1 in which the sink product is screened at a screen size approximating that of said first screening, screen underflow being returned to the separating screen underfiow from the second screening.

nsvm B. oaovs.

tank and the screen overflow being mixed with the 

